How to Winterize Your Sprinkler (Irrigation) System

By Acreage Guide Reviewed October 2026 12 min read

Winterize your irrigation system in the fall, before the first hard freeze. For most homes that means a compressed-air blowout: shut off the water supply, connect a compressor (high volume, low pressure — never above 50 PSI on polyethylene pipe), and push each zone out one at a time until only a fine mist leaves the heads. Then drain the backflow preventer, drain the pump if you have one, and switch the controller to off. Skip it, and the first sustained freeze cracks pipe, splits valves, and hands you a spring repair bill that makes the blowout look free.

The main winterization guide covers your well and septic; this one finishes the job the other article only gestures at — the irrigation lines it told you to "drain and blow out." Most of a blowout is one Saturday morning, or a pro visit of about an hour.

Why this is a one-way door

Water expands as it freezes, and irrigation pipe doesn't stretch. Hunter's own freeze-protection notes put it bluntly: PVC pipe more than half full of water will crack when it freezes, with cracks running fitting to fitting along the length of the pipe. Polyethylene pipe is more forgiving but fittings, valves, sprinkler heads, and the above-ground backflow preventer are not — Hunter says above-ground heads must be drained regardless of what they're made of.

The damage isn't theoretical. A frozen valve manifold or a cracked backflow assembly means digging up and replacing components in spring, when every contractor in town is booked with everyone else's version of the same problem. The fix is cheap and one-directional: get the water out in fall, or fix the damage in spring. There's no mid-winter repair option.

When to do it

Before the first hard freeze — once per year, in fall. That's the industry timing (Angi's 2026 guidance: once per year, ideally just before the first hard freeze) and university extension guidance (the University of Georgia's winterization checklist: preferably before the first freeze).

For the northern tier and the Midwest, irrigation pros are running blowouts through October; for the Mid-Atlantic and mountain West, watch the overnight forecast and don't let a hard freeze beat you by a weekend. Once the ground freezes, a blowout is triage — frozen lines can't be blown out. If you're not sure about your dates, your local extension service's average first-freeze date is the planning number to use.

The three ways to get water out

Not every system needs a compressor. The right method depends on your pipe layout and whether you have check valves (which hold water in low spots and defeat gravity draining).

Method	How it works	Best for
Manual drain	Open drain valves at the low points; water flows out by gravity	Flat yards, no check valves, systems designed with drains
Automatic drain valves	Spring-loaded valves at low points open when pressure drops and drain automatically	Same as manual, but less work each fall — installed at construction
Blowout (compressed air)	A compressor pushes air through each zone, forcing water out the heads	Any system — and required for systems with check valves, since drains can't empty them (per Hunter's freeze-protection notes)

If you have a backflow preventer and a manifold of zone valves, you almost certainly need the blowout. Manual drains only work if the installer put them in and the yard drains toward them.

The blowout, step by step

This is the procedure from Hunter's and Rain Bird's own winterization guidance, plus trade practice from working contractors. Read the safety box below before you touch a compressor.

Shut off the irrigation water supply. There's usually a dedicated shutoff valve for the irrigation system (separate from the house supply). Close it, then run one zone briefly from the controller to relieve line pressure.
Find your blowout point. It should be downstream of the backflow preventer — between the backflow device and the zone valves. Many systems have a quick-coupler key fitting or a hose bib for this. If yours has no blowout port, a pro can add one; don't improvise a connection on the backflow assembly itself.
Open a zone before you add air. Activate the zone furthest from the compressor (or at the highest elevation) from the controller, or open a zone valve manually. Never push air into a closed system — pressure against closed valves is how components break.
Connect the compressor with a pressure regulator in line. Set the regulator to 50 PSI or lower and leave it there. Hunter's guidance: bring pressure up gradually to 50 PSI, and under no circumstances exceed 80 PSI. Rain Bird's manual caps it at 50 PSI flat. The conservative reading wins: 50 PSI default, never above 80.
Blow the zone until the water turns to mist. Heads pop up, water spurts, then the stream breaks into a fine mist. When the mist stops or goes thin, stop and move on — running dry air through gear-drive rotor heads damages them, because the water is their lubricant and coolant.
Repeat for every zone, working back toward the compressor. Open the next zone before closing the one you just finished, so the system is never pressurized with nowhere for air to go. Each zone takes roughly two minutes. Run the whole sequence twice if you have the patience — one pass can leave water sitting in dips and low spots.
Disconnect and shut down. Turn off the compressor and release its tank pressure before disconnecting the hose. Leave zone valves and manual drains open over winter.

Compressor sizing: volume matters more than pressure

Blowouts run on airflow (CFM), not pressure. Rain Bird's winterization guidance calls for a compressor delivering 10 to 25 cubic feet per minute and warns that small shop compressors (2 hp) may not be adequate. Toro's guidance says the same thing another way: the goal isn't high pressure, it's high air volume pushing the water out.

That small pancake compressor in your garage can do a small system with patience — short cycles, full recharges between zones — but a rental tow-behind unit (or a pro's rig) does it in a fraction of the time. The common DIY mistake is the opposite of what you'd expect: cranking the regulator up to 120 PSI to "get it done faster." That doesn't move water faster — it breaks things faster.

Don't forget the backflow preventer

The backflow preventer is the most expensive thing you'll freeze, and it's above ground by design — right in the wind. After the blowout (or instead of one, for the manual-drain crowd):

Drain it, don't blow through it. Close the isolation valves on either side of the backflow device and hook the compressor up downstream of it. Air through the check mechanisms can damage them.
Open the test cocks. Use a flathead screwdriver to open the small test-cock valves on the device so trapped water drains out.
Leave the isolation valves at 45 degrees. Per Rain Bird's winterization guidance: turn both valves to a half-open, 45-degree angle. Fully closed valves trap water between seals; fully open valves leave check assemblies loaded. Half-open drains and rests.
Remove and store any above-ground vacuum breaker you can. If your pressure vacuum breaker unscrews easily, indoor storage beats any cover.

Insulated covers and heat tape help a backflow preventer survive a cold snap, but they're not winterization — on a potable-water connection, they're a delay, not a plan. If the system is idle all winter, drain it.

The pump rule — especially for well owners

If your irrigation runs off a booster pump — or off your well pump — this rule is the whole section: never blow air through the pump. Push the blowout downstream of the pump first, then drain the pump separately by removing its drain plugs. Industry experts state it as a rule: blow the system out downstream, then drain the pump.

Why: a pump full of water freezes and cracks its housing (Rain Bird notes cast-iron pump housings are highly susceptible — trapped water around the impeller expands and destroys the casing), and a pump full of compressed air is a different kind of hazard. For well owners specifically: your blowout point must be downstream of the well pump and pressure tank. Never send compressed air back toward the pump, the pressure tank, or the well itself — that's your drinking-water system, not a lawn accessory. If your irrigation tees off before your pressure tank, call your well contractor before you improvise.

Drip and micro-irrigation systems

Drip lines and micro-sprayers hold less water but have finer passages, and their filters and pressure regulators crack just like anything else. The University of Georgia Extension's winterization checklist covers these systems: drain the filter housings, open flush valves at the low points (automatic drain valves open below about 10 PSI on their own), and pull water from tanks, injectors, and flow meters. If you're fertigating, UGA suggests running a light (2-ppm) chlorine flush through the system before winterizing to clean the lines — and never mix bleach with acids or ammonia, which produces irritating and toxic compounds.

DIY or hire a pro: the honest math

A professional blowout runs $100–$250 for a typical residential system (Angi's 2026 national averages; manual-drain service $75–$150, auto-drain $90–$175). Most quotes cover about six zones, with $10–$20 per additional zone — so a small 1–4 zone system runs $60–$100 and a large 9–12 zone system $150–$250.

What moves the number:

Zone count — the primary cost driver; every zone is blown separately
System size and yard size — more heads, longer pipe runs, more time
Accessibility — buried or hard-to-find blowout ports, valves, and backflow devices add labor
Drip zones and extras — drip, misters, and hose bibs each add steps
Local labor rates — rural and high-cost markets swing both ways
Bundled service — annual contracts covering fall blowout + spring startup usually beat two one-offs

Hire it out when: you don't own or can't rent an adequate compressor, the blowout point is unclear or missing, the system feeds off your well pump and the plumbing is ambiguous, or you simply don't want the liability of 50 PSI in plastic pipe you installed nothing of. Watch and learn this year; do it yourself next year with the right regulator. That first pro visit is also a system audit — good contractors spot the broken heads and coverage gaps while they're running every zone.

When winterizing won't help

Honest limits, as always:

It won't fix a system that was never designed to drain. If there are no low-point drains and no blowout port, the blowout is the whole strategy — budget for a pro, or for having the port added in spring.
It won't protect a system you keep using. If you run the sprinklers into November for a new seeding, winterize after the last run. Every watering after winterization re-fills the lines.
It doesn't replace spring startup. Winterization is half the seasonal cycle. Spring startup — slow-fill the lines, check every head, reprogram the controller — is the other half, and it's when freeze damage you missed shows up.
It won't save the controller electronics from rodents and moisture just by turning it off. If your controller lives in an outdoor box, the enclosure matters more than the switch position.

For the rest of the fall checklist — pump house, pressure tank, wellhead, and the septic side — see how to winterize your well and septic system. For pump problems that turn out not to be freeze-related, walk through well pump and pressure tank troubleshooting.

Frequently asked questions

When should I winterize my sprinkler system?

In fall, before the first hard freeze. In the northern states that usually means October; further south, watch the overnight forecast. Once the ground freezes, lines can't be blown out — the timing is genuinely one-directional. Your local extension service's average first-freeze date is the planning number to use.

Can I blow out my sprinklers with a small air compressor?

Maybe, if the system is small. What matters is airflow (CFM), not tank pressure — Rain Bird's guidance calls for 10–25 CFM, and notes small 2-hp shop compressors may not be adequate. A small compressor can work a few zones with patience (full recharges between zones, short cycles), but for a typical multi-zone system a rental unit or a pro's rig is faster and more reliable.

How much PSI should I use to blow out sprinklers?

50 PSI or lower, with a pressure regulator in line. Hunter's guidance says to bring pressure up gradually to 50 PSI and never exceed 80 PSI under any circumstances; Rain Bird's manual caps it at 50 PSI. High pressure doesn't move water faster — it breaks fittings, launches components, and can injure you.

Do I really need to blow out the system, or can I just drain it?

If your system has low-point drain valves (manual or automatic) and no check valves holding water in low spots, gravity draining can be enough. But most modern systems need the blowout — and Hunter's notes are explicit that systems with check valves to prevent low-head drainage cannot be winterized by drains alone. When in doubt, blow it out.

What happens to the backflow preventer in winter?

If it's above ground and full of water, it freezes and cracks — it's the most expensive single component to lose. Shut off the irrigation supply, drain it through its test cocks, and leave the isolation valves at 45 degrees (half-open) for the winter. Don't blow compressed air through it; connect the compressor downstream of it.

How much does it cost to have sprinklers blown out?

Nationally, a professional blowout averages $100–$250 (Angi 2026 data), with most quotes covering about six zones and $10–$20 per additional zone. It's an annual service — many companies discount it when bundled with spring startup.

Sources

hunterirrigation.com — Hunter Industries LIT-086 Irrigation Notes: Irrigation System Freeze Protection — freeze-crack mechanism and 50 PSI working pressure with 80 PSI absolute ceiling and manual vs automatic drains vs blowout and check-valve systems requiring blowout
manualmachine.com — Rain Bird AZ 85706 user manual compressed-air blowout section — 50 PSI cap and pressure regulator requirement and 10–25 CFM compressor guidance and eye-protection safety rules
fieldreport.caes.uga.edu — University of Georgia Extension CAES Field Report C1094 — drip and micro irrigation winterization including filter draining and flush-valve placement and pre-winterization chlorine flush guidance
www.angi.com — Angi 2026 national cost data — $100–$250 blowout and $75–$150 manual drain and $90–$175 auto drain and $10–$20 per zone beyond about six and once-yearly timing before first hard freeze (market data)
turfmagazine.com — Turf Magazine trade reporting — Hunter's eye-injury and component-launch warnings at 70–80 PSI and never leaving the compressor unattended (corroborates manufacturer safety guidance)
turfmagazine.com — Turf Magazine 9-step procedure — regulator at 50 PSI and zone-by-zone from furthest out and repeat until fine mist and controller to off (corroborates Hunter and Rain Bird procedures)
www.landscapemanagement.net — Landscape Management — Rain Bird and Toro expert guidance on volume over pressure and cast-iron pump drain plugs and about-50-PSI working pressure (corroborates manufacturer specs)
www.lawnandlandscape.com — Lawn and Landscape — industry experts on starting with highest zones and stopping when mist stops to avoid gear-drive rotor damage and never blowing air through the pump (corroborates Hunter and Rain Bird)
www.lawnstarter.com — LawnStarter — 50 PSI poly and 80 PSI PVC guidance and backflow 45-degree valve positions and short-cycle caution on hot compressor air (trade practice corroborating manufacturer limits)
www.mensjournal.com — Men's Journal — Rain Bird senior contractor account manager walkthrough of backflow test-cock draining and 45-degree valve positions and zone-by-zone blowout (corroborates manufacturer procedures)